INVESTIGATING EFFECTS OF GAS FLOW RATE AND CARBON DIOXIDE COMPOSITION IN CHEMICAL ABSORPTION OF CARBON DIOXIDE IN A PACKED BED USING SODIUM HYDROXIDE

摘要

In recent years, the removal of CO_2 from industrial gas streams has become mportant.This has resulted from the environmental concern for reduction of greenhouse as emissions from industrial sources. Here, CO_2 is considered to be the largest ontributor to the global warming problem, and is thus the major target for reduction. The emoval of CO_2 from gas streams can be achieved by absorption into a liquid solvent. his separation process usually takes place in the columns packed with packing aterials to promote direct contact between irrigating liquid and the continuous gas hase, in this study simulation of carbon dioxide absorption by Sodium Hydroxide olution in a packed bed has been investigated. first, mass and energy balances were applied around a differential height of the bed. So, the governing equations were obtained. These equations are related to both phases: gas phase and liquid phase. Gas phase consists of carbon dioxide and air which we just consider carbon dioxide in the equations. On the other hand liquid phase consists of sodium hydroxide, water and sodium carbonate. So we have a general differential equation for each phase and one equation for each substance in both phases. Surface renewal theory by Danckwerts was used to represent the mass transfer operation. The differential equations we obtained should be solved to represent the exit concentration of carbon dioxide in gas phase. Since half of the boundary conditions were not known we used shooting method to estimate these boundary conditions and fourth order runge-kutta method was used to solve the differential equations by MATLAB software. A verification of model was carried out by comparison with the experimental data taken from the packed bed. Gas samples were analyzed by gas chromatography. The predicted results and actual data represent an appreciable agreement.